Method and arrangement for segmentation of a stream of a liquid medium conveyed by a peristaltic pump

ABSTRACT

A programmed discharge of a liquid medium conveyed by a peristaltic pump and segmented by segmentation pistons of a segmentation medium introduced into the stream of this liquid medium is achieved by connection of a blinded hose filled with auxiliary medium to the tubing conveying the segmentation medium, with means for periodically compressing and releasing said blinded hose, thus periodically increasing and decreasing the pressure of the segmentation medium according to a preselected programm.

United States Patent Hrdina 1 Feb. 12, 1974 METHOD AND ARRANGEMENT FOR[56] References Cited SEGMENTATION OF A STREAM OF A IT STATES PATENTSLIQUID MEDIUM CONVEYED BY A 3,524,366 8/1970 Hrdina 137/154 PERISTALTICPUMP Inventor: Jii'i Hrdina, Prague, Czechoslovakia Assignee:Ceskoslovenska akademie ved,

Prague, Czechoslovakia Filed: Feb. 18, 1972 Appl. No.1 227,382

Foreign Application Priority Data Feb. 22, 1971 Czechoslovakia 1309/71US. Cl 137/154, 137/566, 417/477 Int. Cl. F02b 43/12 Field of Search137/1, 154; 417/475, 477;

Primary ExaminerAlan Cohan Attorney, Agent, or FirmMurray Schaffer [57]ABSTRACT A programmed discharge of a liquid medium conveyed by aperistaltic pump and segmented by segmentation pistons of a segmentationmedium introduced into the stream of this liquid medium is achieved byconnection of a blinded hose filled with auxiliary medium to the tubingconveying the segmentation medium, with means for periodicallycompressing and releasing said blinded hose, thus periodicallyincreasing and decreasing the pressure of the segmentation mediumaccording to a preselected programm.

9 Claims, 14 Drawing Figures PAIENIEBFEB 1 21:11

sum 2 OF, 6

PATENIED FEB I 2 i974 sum 3 [1F 6 METHOD AND ARRANGEMENT FORSEGMIEN'IATION OF A STREAM OF A LIQUID MEDIUM CONVIEYED BY APERISTAIL'IIC PUMP BACKGROUND OF THE INVENTION This invention relates toa method and to an arrangement for segmentation of a stream of a liquidmedium conveyed by a peristaltic pump by introducing segmentationpistons into the stream of this medium. The invention relatesparticularly to multichannel peristaltic pumps, provided with correctionmeans for improvement of the uniformity of delivery or of theproportionality of delivery between individual channels of a peristalticpump, but is not limited to pumps having said means.

The invention aims at removal of the drawbacks of peristaltic pumps,particularly to the removal of the non-uniformity of the deliveredstream of the medium, the speed of which varies to a high degree,sometimes even so that it achieves for short periods high negativevalues and further unwelcomed positive and negative accelerations.Another drawback of known pumps is the inaccuracy of the formedsegmentation pistons causing not only an irregular segmentation, butsometimes even fragmentation of segmentation pistons, whichsegmentations are generally gas bubbles, causing great difficultiesAnother drawback is the impossibility of or at least difficulty inprogramming the stream of media conveyed via different channels of thepump.

Attempts have been already made to improve the accuracy of the segmentedstream. One of these arrangements comprises valve means called generallya bar. The bar acts by closing and opening periodically the hoseintroducing segmentation gas into the stream of a liquid medium. Thisarrangement, even if it represents a substantial improvement over theearlier conditions, does not meet the high demands placed on thesegmentation of a stream of a medium for the most up to date analyzers,since this bar closes the passage of gas in a single place, so that thegas is compressed between the bar and between an advancing occlusionorgan of the peristaltic pumps, which is generally a roller. At themoment the bar is lifted, the earlier completely accluded hose is notinstantly made free, but is released only with a cetain residual degreeof nonuniformity. As a result the occluded profile opens with a smallirregular delay with respect to the lifting of the bar. It is thereforeimpossible to achieve by this method an accurate synchronization withthe position of individual rollers of the peristaltic pump. A rathermore imporatant drawback is the circumstance, that after opening theoccluded place the accumulated gas expands with a high speed, so that itenters the stream of the liquid medium as a bubble practically shot intothis liquid medium at a high initial speed. This generates high positiveand negative accelerations of the liquid in the neighbourhood of thesegmentation place, leading frequently even to oscillations whichsubsequently decrease to zero or to the pumping speed of the roller ofthe peristaltic pump. The duration of this phase depends on the time ofopening of the hose between individual occlusions, caused by pressure ofthe bar.

SUMMARY OF THE INVENTION It is an object of this invention to eliminatethese drawbacks and to provide an arrangement capable of formingsegmentation pistons in a stream of a liquid medium with highregularlity and accuracy of segmentation, so that individual sections ofthe liquid medium between two subsequent segmentation pistons would besubstantially equal.

It is another object of this invention to enable an effi cientprogramming of delivery of the segmented medium alternately to achieve auniform delivery which in fact is a special case of a programmeddelivery.

Bearing these and other objects in mind, periodical reciprocal pulses,generated by cyclically repeated oppositely acting effects of adischarged and sucked on auxiliary medium are superposed on a programmedstream of the segmentation medium, whereby the length of the dischargephase of the auxiliary medium may be advantageously a multiple of thelength of the suction phase. In a preferred embodiment a blinded hosefilled with an auxiliary medium, periodically compressed and released bya mechanism is provided. The length of the compressing phase is amultiple of the length of the release phase. The blinded hose isconnected to the hose for introduction of the segmentation medium intothe stream of the liquid medium.

DESCRIPTION OF DRAWINGS Several examples of embodiments of the object ofthis invention are shown in the accompanying drawings, where FIG. Irepresents an elevation of the main parts of a known peristaltic pump,parts of which are in section, FIG. 2 is a similar view of known valvemeans, called generally bar for closing and opening a hose conveyinggas, FIG. 3 is a longitudinal partly sectional view of a peristalticpump provided with improvements according to this invention, FIG. 41 isa similar view with an alternative arrangement of the object of thisinvention, FIG. 5 a cross sectional view of the arrangement shown inFIG. 3, the section being taken along a plane, indicated in FIG. 3 byV-V, FIG. 6 shows in a similar view a still other embodiment of theobject of this invention, FIG. 7 is a schematic layout of a peristalticpump with its principal accessories showing the interconnection with thearrangement according to this invention, FIG. 8 an illustration of thecourse of a reciprocal pulse, FIG. 9 the course of delivery of thesegmentation medium, FIG. 10 the resulting course of the segmentationmedium, FIG. 11 the course of de livery of a liquid medium which has tobe segmented, FIG. I2 the resulting course of the segmentation medium,FIG. 13 a sectional view of an arrangement for mixing a liquid, suitablefor application of the object of this invention and FIG. 14 means forrefilling and emptying the device from FIG. I3 in partly sectional view.

DESCRIPTION OF PREFERRED EMBODIMENTS FIG. 1 shows the principalarrangement of a known peristaltic pump.

Correction extensions 2 and 3 are joined to the pump base I. The pumpmechanism consists of a system of pressure rollers 4, 5, 6, '7 guidedand driven along a closed track 8 in the direction of the arrow I0 bytwo link chains at both sides of the pressure rollers. One or more hoses9 are supported by the pump base I and by its extensions 2 and 3. Thehoses 9 are occluded by the advancing pressure rollers 4, 5, 6, and 7.In order to achieve a full occlusion, it is sufficient only if at leasttwo pressure rollers, for instance 5 and 6 are compressingsimultaneously the hose 9 against the planar base 1. The upper surfacesof the correction extensions 2 and 3 are shaped according to therequired program of delivery of the medium. The medium passes throughthe hoses 9 so that there is superposed on to the uniform movementgenerated by a uniform rolling of a roller, for instance roller 5 alongthe pump base .i the suction effect generated by the subsequentlyreleasing occlusion. This occlusion terminates for instance just at theplace where the roller 7 is shown. From this point on any movement ofthe roller '7 in direction of the arrow has no influence on the deliveryor on the backsucking of the hose 9. The rollers are spaced at mutualdistances L. The correction extension 2 is for the shown arrangement atthe suction side, while the cor rection extension 3 is on the deliveryside of the pump. A correction effect can be achieved even if the uppersurfaces of the correction extensions 2 and 3 are linear but a moreperfect programming, particularly a uniform delivery is achieved bysuitably shaping the upper surface of the correction extension 3. Thiscorrection extension 3 can be shaped individually for each profile ofthe hose 9, which profiles need not be the same. In addition, thecorrection extension 3 can be finely adjusted by adjusting screws Ill,12,.

It is possible to achieve, by a suitable shape of the upper surface ofthe correction extension 3 for any hose 9, an arbitrary variableprogrammed delivery within one cycle of operation of the pump. Theprogrammed delivery is determined within limits by the suction effect ofthe pressure roller, which releases the hose 9 starting from the placeof maximum occlusion (indicated by the position of roller 6) up to thelast point of contact of the roller with hose 9 (indicated by theposition of roller 7).

It is thus possible to segmentate by a similarly arranged pump a mediumfor instance for analytical or other purposes, which medium will becalled in the following the liquid medium. The stream of this liquidmedium is segmentated by introduction of segmentation pistons into thestream of the liquid medium. The segmentation medium is generallygaseous, for instance air, but it can be equally a liquid. in thedescribed arrangement of a peristaltic pump, for instance a liquidmedium is conveyed in one hose 9 while in another parallel hose 9 thesegmentation medium may be conveyed by means of the same mechanism ofthe peristaltic pump. It is obvious that a number of similar hoses 9 canbe arranged side by side in a single pump. Modern peristaltic pumps haveup to 28 hoses controlled by a single mechanism.

It is frequently desirable that the length of a segmentation piston,that is, the length of a bubble have only a small fraction of the lengthof the liquid segment in order to achieve optimum conditions for thehighest accuracy of segmentation. It is of course necessary in suchcases to introduce the segmentation medium into the stream of the liquidmedium at accurate time intervals according to a predeterminedprogramming. The re-solution of the program is one of the principalobjects of this invention. The speed of the stream of the liquid mediumchanges thereby so that the segmentation medium is introduced into theliquid medium at moments, where the speed of the liquid medium is aminimum, and if possible zero. The resulting volume speed of the commonstream after introduction of the segmentation medium into the liquidmedium may be constant, so that the resulting segmented stream willadvance behind the place of segmentation with uniform speed and withoutany jerks, which are present known arrangements and which are thesources of many draw- 5 backs.

The length of a segmentation piston (of a bubble) should be, at normaltemperature, about one-tenth to one-twentieth of the length of a liquidsegment. The ratio of cross sections of hoses for the supply of thesegmentation medium and of the segmented medium is generally in a rangeof l to 10 up to l to 20. It has been however found that due to verysmall diameter of the hose by which the segmentation medium is supplied,which for technological reasons has in addition a very widemanufacturing tolerance, it is rather difficult to obtain a sufficientlyquick suction effect, generated by release of the full occlusion, inorder to comply to the optimum formation of a segmented stream even ifshaped correction extensions are used as indicated in FIG. 3.

A solution has been proposed to synchronize exactly the formation ofsegmentation pistons (bubbles) with the operation of a peristaltic pumpby means of a valve, which alternately closes and opens the hosesupplying air. This solution is object of the U.S. Pat. specificationNo. 3,306.229 and as earlier indicated is generally called bar.

P16. 2 shows one of known embodiments of a bar. The bar is substantiallya cylindrical rod 13 which compresses the hose 9 supplying segmentationair up to a full occlusion against an anvil block 14 by pressure of aspring 115 acting on one arm of a bell crank lever 16, the other armcarrying the rod 13. The bell crank lever 16 is pivotable around thebolt 17 and its lower arm supports a roller 18 engaging with a cam 19rotating on a shaft 20 in synchronism with the mechanism of the pump,controlling the movement of pressure rollers. The extension 21 of thecam 19 causes the roller 18 to recede, lifting thus the rod 13 at acertain predetermined moment, determined by the position of the rollerof the pump. Thus the hose 9 is released for a certain interval time.The air which has been compressed in the meantime between the rod 13 andthe advancing roller of the pump escapes into the part of the hosebehind the rod 13 and into the tubing conveying the liquid medium.

The bar has many advantages and represents a substantial improvementover earlier arrangements. lt however has still some drawbacks. Anaccurately seg mented stream cannot be achieved by means of the bar. Bythe sudden release of the segmentation gas, which had collected in thecourse of the closing of the bar, the gas enters the liquid medium athigh speed. This causes frequent irregularities leading to afragmentation of the bubbles, so that there is a danger that bubbles arecreated not only at the required place for introduction of thesegmenation medium, but also at other places behind the segmentationplace, for instance at the junctions of individual tubings and similarplaces.

FIG. 3 shows schematically an advantageous arrangement according to thisinvention. It represents only the right part of the pump according toFIG. 1 in enlarged scale, and comprising additional elements. Thepressure rollers 6, 7, advance in direction of the arrow 10 along thedot and dash line if and cause a deformation of the hose 22 which issupported by a correction extension 23 of the indicated shape, which issomewhat different from the shape of the correction extension 3 in FIG.l. The hose 22 is on its left end bent downwards and closed or blindedby a plug. This shape allows not only the closing of the left end of thehose 22 but simultaneously by means of a screw enables its fixing to thecorrection extension 23. This correction extension 23 rests by means ofthe left side of said plug 24 against the pump base 1.

This arrangement of the hose 22 and of the correction extension 23 is ofcourse only one of numerous possible arrangements taking differentshapes. The substantial feature is, that the hose 22 is at its endclosed by any suitable closing means and fixed so that it can not beshifted with respect to the correction extension 23 even in the courseof advance of the pressure rollers 6,7.

Another possible embodiment is shown in FIG. 4 where the correctionextension 23 is somewhat wider than the hose 22 and is arranged so thatthe blinded hose 22 passes through a recess provided both in in thecorrection extension 23 and in the pump base 1. The end of the hose 22is here fixed by a screw 26 by means of a washer 27 and issimultaneously closed by pressure against the extended part 28 of thecorrection extension 23.

The position of the correction extension 23 can be adjusted in both thearrangement according to FIG. 3 or FIG. 4 by adjusting screws 11, I2.The correction; extension 23 is pulled the direction of the arrow 29 tothe left, for instance by a spring 30 fixed with one end on thecorrection extension 23 and with the other end for instance on a stableunit 31 of the adjusting screw 12 or on any other stable part of thepump.

The hose 22 continuous further to right (see FIG. 3 and 4) up to theplace of the periodic utilisation of the reciprocal pulses of the mediumwithin the hose as will be described later, either freely, or asindicated in FlG. 3 by being connected by a coupling 32 to a narrowercoupling hose 33. The coupling 32 can be fixed by a screw 34 to theextended right end of the correction extension 23. Thuus not only aperfect fixing of the hose 22 on the right. end of the correctionextension 23 is achieved, but also a more rigid transmission of themediumby means of the narrower hose 33 to the place of utilisation ofthe reciprocal pulses.

It is thus obvious that the starting parts of the hose, indicated by theletter N, which is at the place of the first contact of the hose withthe occluding pressure roller 6, is in a steep direction with respect tothe track of the occluding roller 6. The roller ti is, at this place,parallel with the upper surface of the pump base I. The hose is bent,behind this steep first part N, around the apex of the correctionextension 23 and the following part B of the hose proceeds from thisplace so that it slowly recedes with respect to the track of the roller6 in direction of its advance.

In FIG. 4 it is indicated in broken lines, how it is possible to reducethe length of the delivery part of the periodical delivery curve or ofthe back sucking of the medium from the hose 22. The hose 22 shown inbroken lines is fixed by an extended washer 2'7 obtaining thus the shapeindicated by broken lines so that the first contact of the roller 6 withthe thus deformed hose is not accomplished at point B, but at point 3,.Point B corresponds to the center of the roller 6 at S instead of theoriginal center 8, of the roller 6 shown in full lines.

Thus the track, along which the delivery from the hose 22 isaccomplished and therefore also the time of delivery is reduced forabout the distance between S and S2.

FIG. 5 shows schematically a cross sectional view of the arrangementalong a plane VV indicated in FIG. 3. The pump base I has severalgrooves 36, 37, 38 receiving individual hoses of the pump which may havedifferent profiles. For current designs of pump these grooves aregenerally of the same width and each contains a single hose. Some ofthese grooves however, for instance groove 33 can be wider either toenable the use of a correction extension according to FIG. 4 or toprovide space for two separate or mutually cemented hoses 39, 40 asindicated for groove 37. If hoses 22 are enployed which have to serve apurpose described in the following, they may be fixed by a common screwas for instance shown in FIG. 4 by the screw 26 and their other ends,may be even connected eventually together with other hoses to a commondischarge tubing as shown in the right part of FIG. 3.

The pump base l is provided on its right and left lateral borderprovided with ledges 41, 42 (FIG. 5) limiting the maximum deformation ofindividual hoses due to pressure of the pressure rollers. The wallthickness of hoses of different profiles is equal, so that for a correctocclusion the gap between the pressure roller and the support of thehose has to be somewhat smaller than the height of the ledge 41 or 42increased by the depth of the groove 36, 37 or 38.

FIG. 6 shows another embodiment of this invention enabling to obtainapproximately the same results as the embodiments in FIG. 3 and 4. Abell crank lever 44 is pivotably supported on a bolt 43, the lower endof one arm of this lever provided with a roller 45 engaging with a cam46. A set screw d7 rests on the end of the other arm of lever 44,against a jaw 43 pivotably supported by the bolt 43. This jaw 48 couldbe also firmly connected with the bell crank lever 44. The earliermentioned arrangement however has the advantage of being adjustable. Thejaw 48 rests with its operating part 49 on the hose 22, which issupported by the active surface 53 of an anvil block SI having asomewhat different shape from the shape of the correction extension 3.This shape, indicated in FIG. 6 enables a fixing and closing of a shorthose 22 by a screw 52 by means of a washer 53. The jaw 48 need not havea planar active surface, which surface can be shaped also in some otherway. A spring 54 acts on the bell crank lever 44, generating pressure ofthe jaw 48 against the hose 22 and compressing this hose 22.

The cam 46 rotates in synchronism with the movement of the pumpmechanism and by its action the jaw 48 is released from and pressedagainst the hose 22. The hose 22 can also in this case be connected to athinner hose 55 brought up to the place of utilisation of the periodicpulses, as will be described later.

FIG. 7 shows schematically the interconnection of the different elementswith a peristaltic pump. The peristaltic pump P is provided with anumber of pressure rollers V. Only two hoses conveying the respectivemedia are shown in order not to complicate the drawing. A hose M isprovided for the transport of the liquid medium, the stream of whichshould be segmented by the bubble generator B by a segmentation medium(for instance air) which is equally transported by the peristaltic pumpover the hose S.

The pump is provided with the arrangement according to this invention,indicated by the letter K, where a hose U is located, corresponding tohose 22 or 33. As shown in FIG. 7, this hose is closed on the left endand terminates at its right end at place E into a hose S conveyingsegmentation air. From the junction place E of the hose S with hose Uthe tube T leads to the bubble generator B, where it meets hose Mconveying the liquid. Tubing II starts from the bubble generator B,conveying the resulting segmented stream.

The described arrangement operates as follows; Let us consider thearrangement according to FIG. 7, where the alternative according to FIG.3 is used. Two pressure rollers 6 and 7 are shown in full lines spacedfrom each other a distance L. According to FIG. 3 the pressure roller 6,due to its movement to the right, starts to deform the hose 22 and tosqueeze out the medium contained therein into the connecting hose 33. Inthe following the medium contained in hose 22 is called the auxiliarymedium although this auxiliary medium may be the same as thesegmentation medium, conveyed through the hose S according to FIG. '7.The roller 7 is in FIG. 3 shown in a position, where it just finished todeform hose 22.

In order to finish any contact of the pressure roller with the hoseexactly in this position (in cases, where there is some special reason,this contact may end at some other place), the position of thecorrection extension 23 may be adjusted by the adjusting screw 11.

Two other intermediate positions which the pressure roller 6 maysubsequently occupy, prior to reaching the position indicated by thereference mark 7, are shown in broken lines in FIG. 3. In position thepressure roller 6 generates, along a relatively short track, a maximumdeformation of the hose 22 and thus squeezes out of this hose a maximumamount of auxiliary medium. It does not matter thereby, whether thedeformed upper wall of hose 22 fully contacts the bottom wall and thusfully occludes this hose. It is generally supposed that no fullocclusion takes place. These conditions can be finely adjusted by theadjusting screw 12 practically independently of the position of theadjusting screw 11 and thus also on the position, where the pressureroller in position 7 comes out of contact with hose 22. The axis of theadjusting screw 11 is therefore approximately coincident with aperpendicular line to the track of the pressure roller 7 at the place,where it leaves the hose 22.

The movements of the adjusting screw 11 similarly will not affect themaximum deformation of hose 22 if the adjusting screw is not in aposition shown in FIG. 3 but somewhat shifted to the right as shown inFIG. 4 so that its axis passes through the apex 56 of the correctionextension 23 and thus also through the axis of the pressure roller in aposition indicated by St). At this point the pressure roller 6 achievesthe maximum deformation and thus also the maximum discharge of theauxiliary medium from the hose 22.

In order to achieve a still greater independence of the position of themaximum deformation and thus also of the discharge of the auxiliarymedium, the position of the meeting place 57 between the pump base Itand the correction extension 23 can be shifted more to the right. Inthis manner it would be equally along the axis of the screw 12 passingthrough the apex 56.

FIG. 8, 9, 10, 11, K2 are diagrams showing the time course of themovement of different media in different hoses. In FIG. 8 the full curveshows the time course of the amount Q of the auxiliary medium, which issqueezed from hose 22 in dependence on time t. The curve starts from azero value 0 at the moment where the pressure roller 6 starts to deformhose 22, whereas the pressure roller 7 has just left hose 22, asindicated in FIG. 3. In the course of the movement of the pressureroller 6 to the right. the deformation of hose 22 starts and thus alsothe discharge of the auxiliary medium, as indicated by the steep part Uof the curve between points 0 and X in FIG. 8. This curve is initiallyconcave, because the hose 22 has a circular cross section. The firstpart of the deformation starts therefore with zero speed. It increasesand reaches a maximum at the apex X which corresponds to position inFIG. 3. From this place on, the pressure roller 6, subsequently releasesthe hose 22 until all deformation ceases. This latter point correspondsto the position of the pressure roller indicated by 7. At this place thecurve U drops again to zero. This course is periodically repeated.

It is also possible to consider the movement dependent on the angulardeviation of the mechanisms, of the common driving motor or similardevice. This holds of course true if we suppose that for instance thehysteresis lag behind the static case. This case, which proceeds atinfinitely small speed, can be neglected. The curve U again has betweenits maximum X and its minimum Y a somewhat concave course as indicatedin FIG. 7 by the full line, assuming the active upper surface of thecorrection extension is planar. This surface can have any shape,resulting of course that within limits not surpassing the maximumdeformation of the hose, a different course of the curve U is obtained,as for instance the course indicated by broken lines both in FIG. 9 and8. The courses of both curves can also be chosen so that the resultingcurve of the combined discharge from both hoses will have the courseindicated in FIG. 10 by the full line, with horizontal parts T This canbe achieved by the combination of both discharges according to FIG. 9and 8, either of the discharges corresponding to full or to brokenlines. The deviations of the curve shown in FIG. 8 are of course forthese condition too large and they should be reduced to one half.

From the above it follows, that the auxiliary medium is first squeezedfrom hose 22 into the connecting hose 33 and further to place E of FIG.7, that is to the meeting place with the hose S conveying thesegmentation medium. In the following operation phase the auxiliarymedium is again sucked back into the hose 22. It is obvious from thecourse of the curve U that the discharge phase between points (I) and xis many times shorter than the suction phase between points x and y.

The full curve S in FIG. 9 shows the time course of the amount of thesegmentation medium passing through hose S according to FIG. 7. Thesegmentation medium can be discharged over a channel of the multichannelperistaltic pump or it can be represented as a sum of amounts of themedium, discharged from several hoses of the pump. In FIG. 9 we assumethat the discharge from these hoses is corrected and is approximatelyuniform as indicated by the full line. There can be of course anothercourse as shown in FIG. 9 by a broken line.

In FIG. 10 the curve T shows the course of the volume discharge afterthe stream of the auxiliary medium from hose U has joined the stream ofthe segmentation medium from hose S. The curve T in FIG. 10 shows thatthe discharge pulse of the curve U is superposed to the correspondingpart of the curve S so that, in the tubing T, a steep increase isproduced within the phase indicated between it and x. From point x topoint y the descending part of the curve U (that is the part relating tosuction of the auxiliary medium back into hose 22) is superposed to thecorresponding part of the curve S so that the resulting course of boththese streams, that is of the stream of the auxiliary medium and of thesegmentation medium in tube 1 is shown by the horizontal part of thecurve marked with T That means, that in the phase between points x and ythe segmentation medium in tube T does not move at all. The furthermovement starts again at y, where the following discharge pulse of thecurve U is superposed to the corresponding part of curve S as has beenalready described. The curve I shows therefore the time course of theamount of the segmentation medium in tube 1.

FIG. l I shows the course of the amount of the liquid medium streamingthrough the hose M. Let us suppose that the stream of this medium isprogrammed so that a delay is caused from point to point x, that is thatthe stream of the medium has within this time interval a zero speed.Thus it would again advance from point x to point at a uniform speed,whereafter another delay takes place.

The stream of the liquid medium from hose M joins the stream of thesegmentation stream from hose I in the bubble generator B (see FIG. 7).From the shown curves it is obvious, that by superposition of the courseof the curves M and T, we obtain course H which is practically linear.This means that the resulting segmented stream in the tube H will bequite uniform. It is obvious that this substantially uniform movement ofthe segmented stream has great advantages over a stream advancingnon-uniformly or intermittently or even with ocassional negative speedas is the case for known peristaltic pumps.

Optimum conditions for a most accurate segmented and uniformly advancingstream are thus created according to this invention. The ratherunfavourable cases are eliminated, where the segmentation medium isintroduced into the stream of the liquid medium, which itself does notmove with uniform speed, sometimes intermittently or even with temporarynegative speeds, so that the individual bubbles are separatedirregularly due to oppositely acting capillary hydrodynamic forces. Thecompetition of both these forces determines the moment of separation ofthe segmentation bubble. The uniformity of such a segmentation in knownarrangements is however rather questionable.

It is of course possible to modify the described ar rangements indifferent ways without departing from this invention. The auxiliarymedium in the hose 22 need not be the same as the segmentation medium,although this case will be most frequent. Since the segmentation mediumgenerally used is air, and it is therefore most convenient to use as theauxiliary medium air. It is however possible to use a liquid asauxiliary medium, which case is schematically indicated in FIG. 6. It isthen necessary to prevent penetration of this auxiliary liquid in thecourse of discharge from the hose 22 into the tubing conveying thesegmentation medium. The liquid auxiliary medium would here contact thegaseous segmentation medium in a meniscus 59, forming the boundary ofboth these media. It is important that the discharge track 60 alongwhich the meniscus 59 advances from its starting position when the hose22 is compressed, up to the extreme discharge position s11 should beless than the distance 62 from the 5 starting position of the meniscus59 to the place 63, where the hose 33 meets the tubing S conveying thesegmentation medium. It is obvious that also in case a liquid auxiliarymedium 58 is used this medium performs only a return movement in thehoses 22 and 33 and thus generates the required pulses.

The jaw 58 need not have a planar active part 49 in the arrangementaccording to FIG. 6, this part can be shaped differently and the profilemay be according to a curve of the required shape. It is also possiblethat it be cylindrical similarly as the rod 13 of the known bar. Theknovm bar has of course nothing common with the arrangement according toFIG. 6 as the above description clearly shows, for the bar serves onlyto produce a full occlusion of the hose, whereas the arrangementaccording to FIG. 6 to generates periodic pulses in a blinded hose 22which pulses are transmitted to the segmentation medium.

The arrangement according to this invention can be also used forgeneration of a non-uniform stream of a segmented medium. The mediumneed not have a uniform speed as has been supposed for the embodimentdescribed in connection with FIGS. 8 to 12 but may be programmedarbitrarily. The required course of the resulting segmented medium isthereby achieved by superposing a partial programmed course ofperiodical discharge and suction of the auxiliary medium in hose 22 to aprogrammed gradual discharge of the segmentation medium in the tubing S(FIG. 7). This combined discharge course is superposed to the programmedgradual discharge of the liquid medium, passing through tubing M. It issubstantially the same operation as described with reference to FIG. gto I2with the difference that the result should not be a uniform, but adifferently programmed stream. The individual partial programming isobtained by a suitable shape and inclination of the correctionextensions 3 and 23 controlling the passage of the media through hoses 9and 22.

Although the arrangement has been described in connection with pressurerollers of a peristaltic pump, it is obvious that any other mechanismwhich produces the required course of the pulses can be used for thispurpose instead of said rollers. I

The arrangement according to this invention can be also used for otherpurposes, such as for arrangements, where multichannel peristaltic pumpswith or without a bar proved to be advantageous at laboratorium equipments. These known pumps can be easily adapted by adding the arrangementaccording to this invention and thus improve their performance or adjustthem for other purposes as will be described later.

It is obvious from the foregoing, that optimum effects may be achievedwith the arrangement according to this invention, which removes to ahigh degree some major drawbacks of peristaltic pumps. Peristaltic pumpshave met recently with objections, since it looked that these drawbackswould be major factors in the future and would limit the furtherdevelopment of devices using these pumps. Furthermore, it was notcontemplated that their advantages would not in the future surpass theirdisadvantages, which have been considered to be irremovable. Accordingto this invention these drawbacks have been to a large extent elimiiiinated and thus the use of peristaltic pumps, even for the most up todate analyzers, is enabled.

Everything what has been said and shown for peristaltic pumps havingpressure rollers guided by link chains as occlusion organs holds truefor practically all kinds of peristaltic pumps. This concernsparticularly frequently used pumps, where the hoses are supported by atlewt partly circular tracks. The arrangement according to this inventioncan be aslo used for achievement of similar useful effects incombination with non peristaltic pumps, even with piston pumps.

The method and arrangement according to this invention can be alsoapplied for other purposes without a pump, for instance for mixing ofliquids. A similar arrangement is indicated schematically in FIG. 13. Avessel having for instance the shape of a test tube contains some liquid65 which has to be stirred. A tube 66 is connected for instance to ahose 33 as in FIG. 3 or to a discharge tube of any of the describedarrangements. The tube 66 terminates with its narrowed discharge crosssection below the level of the liquid 65. In operation, the liquid 65 issucked on into the tube in the course of the suction phase in the hose22, whereafter it is discharged back into the vessel 64 with highdischarge speed in the course of the short and vehement discharge phase,causing an efficient mixing of the liquid. if a liquid acting asauxiliary medium is in the tube 66 or in its end part care should betaken that this auxiliary medium does not enter via the tube 66 thevessel 64, that is its meniscus must not come close to the end of tube66. It is thus possible to achieve a mixture of the liquid 65 withoutcontact with the gas, where the bubbling through the liquid could betroublesome.

A similar arrangement is frequently necessary for mixing of samples,particularly of samples which have a tendency to sediment, for instanceblood corpuscles. This task is now generally performed by means ofvibrators or by bubbling through of a gas. A multichannel peristalticpump generally is available at automatic devices operating in differentlaboratories, particularly in laboratories working with biologicalmaterial. The application of the arrangement according to this inventionfor similar automatic devices presents no particular difiiculties foradaptation.

The tube 66 shown in FIG. 13 which is for the sake of simplicity drawnas a simple tube for mixing, can be combined with a known needle or tubefor sucking on a sample from the vessel 64 for the proper automaticanalytic processing, using eventually known methods, by means of whichthe sucking on is achieved so that the segmentation is created veryclose to the lower end of tube 66.

These possibilities and other possible useful combinations of the methodand arrangement according to this invention with known and currentlyused methods and arrangements are rather numerous and their applicationwill offer no difficulties to those familiar with these branches theywill he therefore neither described nor shown on drawings.

It is however advantageous, if the content of the vessel 64 in FIG. 13can be refilled with the liquid so that the vessel 64 is not closed asindicated in FIG. 13 but for instance as shown in FIG. 1 This is nostrict condition but an advantage, having its significance in practicaloperation as the filling of this sack" in a closed condition is somewhatmore difficult.

According to the embodiment in FIG. 14 the bottom of this sack is madeso that its blinding plug 67 has the indicated shape, having acommunication opening 68, into which a needle 69 is terminating, tightlyfixed in the plug 67. A resilient hose 70 is connected to this needle69, which is on a place suitable for manual operation closed by any kindof pressure device, symbolically indicated by a screw 71. The hose 70proceeds further and its free end can he slipped either directly or viaan injection needle to an injection syringe 72 filled with a suitableliquid, generally water.

After the closing screw 71 has been loosened, the liquid content of thesyringe 72 can be pressed via the thin hose 70, the needle 69 and theopening 68 into the proper space of the sack of any shape. It isunderstood that after filling and tightening of the closing screw 71 theliquid content remains unchanged and may be eventually completed orreplaced by some other liquid after prior emptying by repeated fillingof the injection syringe 72 with air. Thereafter the sack can berefilled with another liquid. Thus it is possible to regulate or tocomplete the content not only of the sack but also of the hosesconnected thereto. It is sometimes advantageous, for the liquid contentwhich is periodically discharged and again sucked on by the proper sackreach close to the junction place with the constantly streaming mediumto be segmented, as for instance shown in FIG. 7, whereby theperiodically by the sack sucked on and discharged liquid content mayreach up to the hose 33 and into the neighbourhood of its junction withhose S of the block F. If for any reason the liquid from the sack" wouldreach beyond the junction place of both channels in block E, the surplusof the liquid would be automatically taken along over the tube T to thesegmentation placed in the bubble generator B.

I claim:

1. A system for the segmentation of a stream of a liquid medium conveyedby a peristaltic pump, through the introduction of segmenting pistons ofa segmentation medium into the stream of said liquid medium comprising aperistaltic pump having a base supporting flexible hoses conveying therespective medium and occlusion organs adapted to perform a relativemovement with respect to said base causing, by successive compression ofsaid flexible hoses, a movement of these media in said flexible hoses afirst of said flexible hoses containing a liquid medium to be segmenteda second of said flexible hoses containing a segmentation medium,

both said streams of these media meeting at a segmentation place,

a third of said flexible hoses blinded at one end and containing anauxiliary medium connected to the second hose conveying the segmentationmedium, and

means for periodically generating a compression and release of saidthird flexible hose.

2. The system as set forth in claim 1, wherein the release phase of saidthird flexible blinded hose is a multiple of its compression phase.

3. The system as set forth in claim 1, wherein the third blinded hose issupported by a correction extension of said pump base so as to be in thetrack of the occluding organs of the peristaltic pump, the part of saidthird blinded hose near the blinded and being steeply inclined withrespect to the track of the occluding organs, the following part of saidthird blinded hose gradually receding from said track in the directionof movement of the occluding organs, and the surface of the correctionextension supporting the blinded hose being curved near the pump base.

4. The system as set forth in claim 3, wherein the correction extensionis provided with means for adjustment of its position with respect tothe track of the occluding organs.

5. The system as set forth in claim 4, wherein one of said means foradjustment comprising an adjusting screw situated close to the pump basethe axis of said adjusting screw passing through the apex of the curvedsurface of the correction extension.

6. The system as set forth in claim 1, wherein the blinded hose isconnected to the tubing conveying the segmentation medium 'via aconnecting hose of a smaller diameter and higher rigidity than theblinded hose.

7. The system as set forth in claim 1, wherein the means for compressingand releasing the blinded hose comprises a pressure jaw controlled by acam mechanism.

8. The system as set forth in claim 1, including a tube adapted to beconnected with the open end of the blinded hose, a container filled witha liquid to be mixed, the end of said tube terminating below the surfaceof this liquid. I

9. The system as set forth in claim 8, wherein said container isconnected by a flexible hose with means for emptying and refilling thiscontainer and with means for closing and opening said flexible hose.

1. A system for the segmentation of a stream of a liquid medium conveyedby a peristaltic pump, through the introduction of segmenting pistons ofa segmentation medium into the stream of said liquid medium comprising aperistaltic pump having a base supporting flexible hoses conveying therespective medium and occlusion organs adapted to perform a relativemovement with respect to said base causing, by successive compression ofsaid flexible hoses, a movement of these media in said flexible hoses afirst of said flexible hoses containing a liquid medium to be segmenteda second of said flexible hoses containing a segmentation medium, bothsaid streams of these media meeting at a segmentation place, a third ofsaid flexible hoses blinded at one end and containing an auxiliarymedium connected to the second hose conveying the segmentation medium,and means for periodically generating a compression and release of saidthird flexible hose.
 2. The system as set forth in claim 1, wherein therelease phase of said third flexible blinded hose is a multiple of itscompression phase.
 3. The system as set forth in claim 1, wherein thethird blinded hose is supported by a correction extension of said pumpbase so as to be in the track of the occluding organs of the peristalticpump, the part of said third blinded hose near the blinded and beingsteeply inclined with respect to the track of the occluding organs, thefollowing part of said third blinded hose gradually receding from saidtrack in the direction of movement of the occluding organs, and thesurface of the correction extension supporting the blinded hose beingcurved near the pump base.
 4. The system as set forth in claim 3,wherein the correction extension is provided with means for adjustmentof its position with respect to the track of the occluding organs. 5.The system as set forth in claim 4, wherein one of said means foradjustment comprising an adjusting screw situated close to the pump basethe axis of said adjusting screw passing through the apex of the curvedsurface of the correction extension.
 6. The system as set forth in claim1, wherein the blinded hose is connected to the tubing conveying thesegmentation medium via a connecting hose of a smaller diameter andhigher rigidity than the blinded hose.
 7. The system as set forth inclaim 1, wherein the means for compressing and releasing the blindedhose comprises a pressure jaw controlled by a cam mechanism.
 8. Thesystem as set forth in claim 1, including a tube adapted to be connectedwith the open end of the blinded hose, a container filled with a liqUidto be mixed, the end of said tube terminating below the surface of thisliquid.
 9. The system as set forth in claim 8, wherein said container isconnected by a flexible hose with means for emptying and refilling thiscontainer and with means for closing and opening said flexible hose.